Make sure to read the rules before you bet at a table. Different casinos will have different policies on if the dealer should hit on a hard or soft 16 or 17.The object of the game is to get a score as close as you can to 21 without going over.
In single deck or 2-deck games, the cards are dealt by hand. This means that they will continue to hit until they hit 17 or above. The dealer uses a blank card to signify when it’s time to reshuffle the decks, and if the casino is using more than 4 decks, the cards are dealt from a box called a shoe.
For example, a 10 and a 7 would be a hard 17. However, if you know for a fact they have an ace as their hole card, you should hit anyway because there's no way for you to win or tie unless you increase your score. Therefore, it's best to hit even if you think you'll bust. If the dealer has a hard 17, they have to stand and there's no chance that you can beat them if you have under a 17. One of the most obvious ways to take advantage of a hole card is to hit when you know that the dealer has a hard 17 and you have a worse hand. Hit if you know that the dealer must stand and is beating your hand.